How much do you need to know about the REI process before diving in? On one side, I feel like if you don't know enough then you'll be investing without proper knowledge/won't be prepared, but on the other side, I feel there comes a point where you just need to take action or you won't ever make any deals. What is that point where you need to draw a line and say, "I've learned enough. I can start investing now." (and obviously continue to build upon your knowledge at that point)

You'll know enough when you can define the following:

Riparian rights, homestead exemption, eminent domain, mortgagee/mortgagor, statute of frauds, tenants in common, quit claim vs warranty deed, Garn/St Germain Law, sq feet in an acre, right of first refusal, bundle of rights, fee simple, and the statute of limitations.

Wait--never mind.  That's the stuff you'll never use.  

Better to know market value, rental values, costs of repairs and how to negotiate when you find a motivated seller.  

Or you could just partner with a more experienced investor.